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In 1972, the first SAE paper describing the use of computer simulation as a design tool for automotive air conditioning was written by these authors. Since then, many such simulations have been used and new tools such as CFD have been applied to this problem. This paper reviews the work over that past 35 years and presents several of the improvements in the basic component and system models that have occurred. The areas where “empirical” information is required for model support and the value of CFD cabin and external air flow modeling are also discussed.

This paper presents an analysis of the displacement measurement of the Hybrid III 50th percentile male dummy chest in quasistatic and dynamic loading environments. In this dummy, the sternal chest deformation is typically characterized using a sliding chest potentiometer, originally designed to measure inward deflection in the central axis of the dummy chest. Loading environments that include other modes of deformation, such as lateral translations or rotations, can create a displacement vector that is not aligned with this sensitive axis. To demonstrate this, the dummy chest was loaded quasistatically and dynamically in a series of tests. A string potentiometer array, with the capability to monitor additional deflection modes, was used to supplement the measurement of the chest slider.

Studies show that the pedestrian population at high risk of injury consists of both young children and adults. The goal of this study is to gain understanding in the mechanisms that lead to injuries for children and adults. Multi-body pedestrian human models of two specific anthropometries, a 6year-old child and a 50th percentile adult male, are applied. A vehicle model is developed that consists of a detailed rigid finite element mesh, validated stiffness regions, stiff structures underlying the hood and a suspension model. Simulations are performed in a test matrix where anthropometry, impact speed and impact location are variables. Bumper impact occurs with the tibia of the 50th percentile adult male and with the thigh of the 6-year-old child. The head of a 50th percentile male impacts the lower windshield, while the 6-year-old child's head impacts the front part of the hood.

This research investigates the variation of pedestrian stance in pedestrian-automobile impact using a validated multi-body vehicle and human model. Detailed vehicle models of a small family car and a sport utility vehicle (SUV) are developed and validated for impact with a 50th percentile human male anthropometric ellipsoid model, and different pedestrian stances (struck limb forward, feet together, and struck limb backward) are investigated. The models calculate the physical trajectory of the multi-body models including head and torso accelerations, as well as pelvic force loads. This study shows that lower limb orientation during a pedestrian-automobile impact plays a dominant role in upper body kinematics of the pedestrian. Specifically, stance has a substantial effect on the subsequent impacts of the head and thorax with the vehicle. The variation in stance can change the severity of an injury incurred during an impact by changing the impact region.

This paper presents a computational study of the effects of three parameters on the resulting thoracic injury criteria in side impacts. The parameters evaluated are a) door velocity-time (V-t) profile, b) door interior padding modulus, and c) initial door-to-occupant offset. Regardless of pad modulus, initial offset, or the criterion used to assess injury, higher peak door velocity is shown to correspond with more severe injury. Injury outcome is not, however, found to be sensitive to the door velocity at the time of first occupant contact. A larger initial offset generally is found to result in lower injury, even when the larger offset results in a higher door velocity at occupant contact, because the increased offset results in contact later in the door V-t profile - closer to the point at which the door velocity begins to decrease. Cases of contradictory injury criteria trends are identified, particularly in response to changes in the pad modulus.

Computer simulations, dummy experiments with a new enhanced upper extremity, and small female cadaver experiments were used to analyze the small female upper extremity response under side air bag loading. After establishing the initial position, three tests were performed with the 5th percentile female hybrid III dummy, and six experiments with small female cadaver subjects. A new 5th percentile female enhanced upper extremity was developed for the dummy experiments that included a two-axis wrist load cell in addition to the existing six-axis load cells in both the forearm and humerus. Forearm pronation was also included in the new dummy upper extremity to increase the biofidelity of the interaction with the handgrip. Instrumentation for both the cadaver and dummy tests included accelerometers and magnetohydrodynamic angular rate sensors on the forearm, humerus, upper and lower spine.

Pedestrian finite element models (PFEM) are used to investigate and predict the injury outcomes from vehicle-pedestrian impact. As postmortem human surrogates (PMHS) differ in anthropometry across subjects, it is believed that the biofidelity of PFEM cannot be properly evaluated by comparing a generic anthropometry model against the specific PMHS test data. Global geometric personalization can scale the PFEM geometry to match the height and weight of a specific PMHS, while local geometric personalization via morphing can modify the PFEM geometry to match specific PMHS anatomy. The goal of the current study was to evaluate the benefit of morphed PFEM compared to globally-scaled and generic PFEM by comparing the kinematics against PMHS test results. The AM50 THUMS PFEM (v4.01) was used as a baseline for anthropometry, and personalized PFEM were created to the anthropometric specifications of two obese PMHS used in a previous pedestrian impact study using a mid-size sedan.

Some rollover testing methodologies require specification of vehicle kinematic parameters including travel speed, vertical velocity, roll rate, and pitch angle, etc. at the initiation of vehicle to ground contact, which have been referred to as touchdown conditions. The complexity of the vehicle, as well as environmental and driving input characteristics make prediction of realistic touchdown conditions for rollover crashes, and moreover, identification of parameter sensitivities of these characteristics, is difficult and expensive without simulation tools. The goal of this study was to study the sensitivity of driver input on touchdown parameters and the risk of rollover in cases of steering-induced soil-tripped rollovers, which are the most prevalent type of rollover crashes. Knowing the range and variation of touchdown parameters and their sensitivities would help in picking realistic parameters for simulating controlled rollover tests.

More than half of occupant lower extremity (LEX) injuries due to automotive frontal crashes are in the knee-thigh-hip (KTH) complex. To design the injury countermeasures for the occupant LEX, first the biomechanical and injury responses of the occupant LEX components during automotive frontal crashes should be known. The objective of this study is to develop a detailed biofidelic occupant LEX Finite Element (FE) model based on the component surfaces reconstructed from the medical image data of a 50th percentile male volunteer in a sitting posture. Both volumetric (unstructured) and structural mesh methods were used to generate the solid elements (mostly hexahedral type) to enhance the model simulation accuracy. The FE model includes the femur, tibia, fibula, patella, cartilage, ligaments, menisci, patella tendon, flesh, muscle, and skin. The constitutive material models and their corresponding parameters were defined based on literature data.

The response and risk of injury for occupants in frontal crashes are more severe when structural deformation occurs in the vehicle interior. To reproduce this impact environment in the laboratory, a sled system capable of producing structural intrusion in the footwell region has been developed. The system couples the hydraulic decelerator of the sled to actuator pistons attached to the toepan and floorpan structure of the buck. Characterization of the footwell intrusion event is based on developing a toepan pulse analogous to the acceleration pulse used to characterize sled and vehicle decelerations. Preliminary sled tests with the system indicate that it is capable of simulating a complex sequence of toepan/floorpan translations and rotations.

Effects of a cabin-level humidity upset on an activated carbon column used for adsorption of trace compounds from air are examined through a series of experiments and computer simulations. Breakthrough curves measured for dichloromethane in the presence of water indicate that a rapid increase in relative humidity can displace large quantities of dichloromethane from the adsorbed phase resulting in effluent streams containing more than 20 times the feed concentration. Additionally, the breakthrough time for organic compounds is reduced significantly at high relative humidity. Numerical simulation results show favorable qualitative agreement with measured breakthrough curves, yet do not consistently predict accurate water or dichloromethane loadings at all experimental conditions.

Two sled systems capable of producing structural intrusion in the footwell region of an automobile have been developed. The first, System A, provides translational toepan intrusion using actuator pistons to drive the footwell structure of the test buck. These actuator pistons are coupled to the hydraulic decelerator of the test sled and are powered by hydraulic energy from the impact event. Resulting footwell intrusion is characterized using a toepan pulse analogous to the acceleration pulse used to characterize sled and vehicle decelerations. Sled tests with System A indicate that it is capable of accurately and repeatably simulating toepan/floorpan intrusion into the occupant footwell. Test results, including a comparison of lower extremity response between intrusion sled tests and no intrusion sled tests, indicate that this system is capable of repeatable, controlled structural intrusion during a sled test impact.

The air bag has proven effective in reducing fatalities in frontal crashes with estimated decreases ranging from 11% to 30% depending on the size of the vehicle [IIHS-1995, Kahane-1996]. At the same time, some air bag designs have caused fatalities when front-seat passengers have been in close proximity to the deploying air bag [Kleinberger-1997]. The objective of this study was to develop an accurate and repeatable out-of-position test fixture to study the deployment of air bags into out-of-position occupants. Tests were performed with a 5th percentile female Hybrid III dummy and studied air bag loading on the thorax using draft ISO-2 out-of-position (OOP) occupant positioning. Two different interpretations of the ISO-2 positioning were used in this study. The first, termed Nominal ISO-2, placed the chin on the steering wheel with the spine parallel to the steering wheel.

Steering control devices are used by people who have difficulty gripping the steering wheel. These devices have projections that may extend up to 14 cm toward the occupant. Testing indicated that contact with certain larger steering control devices with tall rigid projections could severely injure a driver in a frontal collision. In order to reduce this injury risk, an alternative, less injurious design was developed and tested. This design, which included replacing unyielding aluminum projections with compliant plastic ones, produced significantly lower peak contact pressure and less damage to the chest of a cadaver test subject, while maintaining the strength necessary to be useful.

Multibody human models are widely used to investigate responses of human during an automotive crash. This study aimed to validate a commercially available multibody human body model against response corridors from volunteer tests conducted by Naval BioDynamics Laboratory (NBDL). The neck model consisted of seven vertebral bodies, and two adjacent bodies were connected by three orthogonal linear springs and dampers and three orthogonal rotational springs and dampers. The stiffness and damping characteristics were scaled up or down to improve the biofidelity of the neck model against NBDL volunteer test data because those characteristics were encrypted due to confidentiality. First, sensitivity analysis was performed to find influential scaling factors among the entire set using a design of experiment.

Some rollover test methods, which impose a touchdown condition on a test vehicle, have been developed to study vehicle crashworthiness and occupant protection in rollover crashes. In ground-tripped rollover crashes, speed, steering maneuver, braking, vehicle inertial and geometric properties, topographical and road design characteristics, and soil type can all affect vehicle touchdown conditions. It is presumed that while there may be numerous possible combinations of kinematic metrics (velocity components and orientation) at touchdown, there are also numerous combinations of metrics that are not likely to occur in rollover crashes. To determine a realistic set of touchdown conditions to be used in a vehicle rollover crash test, a lateral deceleration sled-based non-destructive rollover initiation test system (RITS) with a fully programmable deceleration pulse is in development.

The goal of this study was to evaluate the biofidelity of the three computational surrogates (GHBMC model, WorldSID model, and the FTSS ES-2re model) under the side impact rigid wall sled test condition. The responses of the three computational surrogates were compared to those of post mortem human surrogate (PMHS) and objectively evaluated using the correlation and analysis (CORA) rating method. Among the three computational surrogates, the GHBMC model showed the best biofidelity based on the CORA rating score (GHBMC =0.65, WorldSID =0.57, FTSS ES-2re =0.58). In general, the response of the pelvis of all the models showed a good correlation with the PMHS response, while the response of the shoulder and the lower extremity did not. In terms of fracture prediction, the GHBMC model overestimated bone fracture.

A follow-up case study on rollover testing with a single full-size sport utility vehicle (SUV) was conducted under controlled real-world conditions. The purpose of this study was to conduct a well-documented rollover event that could be utilized in evaluating various methods and techniques over the phases associated with rollover accidents. The phases documented and discussed, inherent to rollovers, are: pre-trip, trip, and rolling phases. With recent advances in technology, new devices and techniques have been designed which improve the ability to capture and document the unpredictable dynamic events surrounding vehicle rollovers. One such device is an inertial measurement unit (IMU), which utilizes GPS technology along with integrated sensors to report and record measured dynamic parameters real-time. The data obtained from a RT-4003 IMU device are presented and compared along with previous test data and methodology.

This study evaluated the response of restrained post-mortem human subjects (PMHS) in 40 km/h frontal sled tests. Eight male PMHS were restrained on a rigid planar seat by a custom 3-point shoulder and lap belt. A video motion tracking system measured three-dimensional trajectories of multiple skeletal sites on the torso allowing quantification of ribcage deformation. Anterior and superior displacement of the lower ribcage may have contributed to sternal fractures occurring early in the event, at displacement levels below those typically considered injurious, suggesting that fracture risk is not fully described by traditional definitions of chest deformation. The methodology presented here produced novel kinematic data that will be useful in developing biofidelic human models.

The objective of the study was to analyze independently the contribution of pre-impact spine posture on impact response by subjecting a finite element human body model (HBM) to whole-body, lateral impacts. Seven postured models were created from the original HBM: one matching the standard driving posture and six matching pre-impact posture measured for each of six subjects tested in previously published experiments. The same measurements as those obtained during the experiments were calculated from the simulations, and biofidelity metrics based on signals correlation were established to compare the response of HBM to that of the cadavers. HBM responses showed good correlation with the subject response for the reaction forces, the rib strain (correlation score=0.8) and the overall kinematics. The pre-impact posture was found to greatly alter the reaction forces, deflections and the strain time histories mainly in terms of time delay.