NIOSH AutoROPS Research to Practice: Zero Turn Commercial Mowers

Marketing new safety devices is a critical function on the research-to-practice path. This path to adoption of new safety technology is not always straightforward. The National Institute for Occupational Safety and Health (NIOSH) Automatically deployable Rollover Protective Structure (AutoROPS) is a passive safety device developed to protect tractor operators in an overturn event. Tractor overturns kill more than 100 farmers each year in the United States (Myers, 2003). This technology was first designed to target the agricultural low-clearance environments involving “low-profile” tractors where traditional ROPS may not be feasible. These tractors are exempted from ROPS use as stated in OSHA 1928.51(b) (5) (i & ii). The upper portion of the AutoROPS remains retracted under low clearance areas but deploys to full height when an overturn is detected. The AutoROPS has been tested under both field and laboratory conditions prescribed in the ROPS performance standard, SAE J2194. To translate successful research into occupational practice, NIOSH formed a partnership with FEMCO, a ROPS manufacturer, in 2003. FEMCO’s efforts found Scag Power Equipment, a zero-turn commercial mower manufacturer. NIOSH has partnered with them as well. The Scag AutoROPS has been successfully laboratory tested to industry standards. Preliminary field evaluations of the deployment system have been conducted in preparation for field upset tests. Product development, test procedures, test results, and current marketing efforts are presented on this innovative safety device.

Risk Analysis and Safety Evaluation of Biomass Cookstoves

Combustion of biomass in open fires and ad hoc unventilated stoves is the primary form of household energy for two to three billion people worldwide. These cookstoves have significant health, social, and economic impacts on poor families in developing countries. These impacts include disease, injury, excess time spent gathering fuel, deforestation, and high fuel costs relative to income. In an attempt to address many of these problems numerous non-governmental organizations have developed several biomass cookstove designs in the past five to ten years. These designs have generally focused on increasing fuel efficiency, and to a lesser degree, reducing particulate emissions. This emphasis has been driven largely by the availability of relatively straight forward fuel efficiency tests for biomass cookstoves developed 10–20 years ago and the ability of researchers to adapt current air pollution testing methods for stoves. In contrast there are no safety standards or hazard evaluations available for biomass cookstoves. Because of this the safety of the cookstove is seldom explicitly considered as a part of the design process. This paper addresses the basic safety issues that should be considered in the design of biomass stoves used in developing countries, describes the reasoning behind these safety issues, and proposes a set of safety guidelines for testing and evaluating stove safety. These guidelines are intended for testing and evaluating in the field as well as in the design lab.

An Evaluation of the Mechanical Behaviour of Imperfect Aluminium Tubes

In this research the effect of geometric changes introduced on Al 6063-T6 circular tubes in the form of horizontal and spiral grooves, (Fig. 2 and Fig. 3) is assessed. The horizontal and spiral grooves were cut into the tube to a depth of half the wall thickness of the tubes, while the pitch was varied for both the horizontal and spiral grooves, and the cut width was kept constant. These tubes were axially compressed, and load vs. displacement and Energy vs. displacement graphs were generated from the captured experimental data for the tubes. A Finite Element Method model is presented for each of the experimentally tested tubes. 2D models for the uncut and horizontally grooved tubes and a 3D model for the spiral cut tube were generated and analyzed. Reaction force vs. displacement and energy vs. displacement graphs are presented for the different analyses. A comparison is made between the numerically and experimentally determined gradients of the energy vs. displacement graphs for each of the tubes analyzed. This forms the basis for an energy absorber design with application in the transport industry currently under consideration.

Reliability Evaluation of BGA Solder Joints by Using Thermal Fatigue Models

The use of Ball Grid Array (BGA) interconnects utilizing the BGA solder joint has grown rapidly because of its small volume and diversity of its application. Therefore, the continuous quantification and refinement of BGA solder joint in terms of its reliability are required. The creep and cyclically applied mechanical loads generally cause metal fatigue on the BGA solder joint which inevitably leads to an electrical discontinuity. In the field application, the BGA solder joints are known to experience mechanical loads during temperature changes caused by power up/down events as the result of the Coefficient of Thermal Expansion (CTE) mismatch between the substrate and the Si die. In this paper, extremely small resistance changes in the lead free joints corresponding to the through-cracks generated by the thermal fatigue were measured and the failure was defined in terms of anomalous changes in the joint resistance. Furthermore, the reliability of BGA solder joints under thermal cycling was evaluated by using a criterion that may define and distinguish a failure in the solder joint. Any changes in circuit resistance according to the accumulated damage induced by the thermal cycling in the joint were recorded and evaluated by the First Order Reliability Method (FORM) procedure in order to quantify the reliability of solder joint. The first order Taylor series expansion of the limit state function incorporating with thermal fatigue models is used in order to estimate the failure probability of solder joints under heated condition. Various thermal fatigue models are utilized in this study. Models based on various plastic-strain rates such as Coffin-Manson fatigue model, total strain fatigue model and Solomon fatigue model are utilized in this study. The effects of random variables such as the CTE, the pitch of solder joint, the diameter of solder joint, and the CTE difference solder joints on the failure probability of the solder joint are systematically investigated by using a failure probability model with the FORM.

Design Recommendations for Controlling the Jam-Clearing Hazard on Recycling Industry Balers

Between 1986 and 2002, there were 43 fatalities in the United States to operators of recycling industry balers. Of these fatalities, 29 involved horizontal balers that were baling paper and cardboard (Taylor, 2002). Balers often become jammed while the baling process is occurring, and the only way to remove the jam is manually. This requires an employee to place a limb of their body into the jamming area and remove the material that is causing the jam. While lockout and tagout procedures reduce the risk of hazardous energy being released, they can still be easily bypassed, ignored, or forgotten. Recent efforts to reduce machine-related injury and death involve the development of a control system for these machines that automatically detects hazardous operating conditions and responds accordingly. The system is being developed at the National Institute for Occupational Safety and Health (NIOSH). This system, JamAlert, automatically terminates the power to the machine when a jam is detected. JamAlert detects a jam by observing both the strain that is experienced by the shear bar of the baler and the hydraulic pressure at which the ram is operating. The strain that is experienced by the baler shear bar when a jam is initiated was calculated in this study through laboratory testing and finite element modeling. Design recommendations are presented on how best to tune the JamAlert’s operating program to most effectively control the jam-clearing hazard.

Evaluation of Deformable Barrier Designs and Associated Compatibility Metrics in Full Frontal Impact Testing

Several modifications to an existing deformable barrier are investigated for their ability to predict the presence of secondary energy absorbing structures (SEAS) using four deformable barrier designs with simulated impact by two vehicles. This study is motivated by the assumption that SEAS may enhance vehicle-to-vehicle compatibility and it is desirable to know if SEAS presence and its benefits are detectable through dynamic barrier testing. The considered barrier types are modifications of the Transportation Research Laboratory (TRL) barrier consisting of two layers, a front and rear. Each layer is 150mm thick with the first (front-most with respect to the vehicle) layer compression stiffness of 0.34 MPa and the second (rear-most) of 1.71 MPa. Proposed modifications to the (original, baseline) barrier are: 1. Increase the stiffness of a localized region of the front layer to 1.71 MPa (between ground heights of 330mm and 580mm). 2. Increase the depth of the second layer to 200 mm. 3. lncrease the depth of the second layer to 300 mm and use a single, non-segmented piece for the entire layer. The resulting four barrier configurations are all assumed to have 125 × 125 mm segmented “cells” supported by load time-history transducers. Computer simulation of impact by four vehicle models differing in mass and structural architecture is used. Four vehicle metrics intended to measure compatibility through impact with deformable barriers are used to quantify each barrier design’s ability to detect SEAS. Using the metrics outlined in this paper, a barrier design with stiffened rows three and four is best suited for SEAS detection. This conclusion is based on its sensitivity to four vehicle designs with and without SEAS as well as consistency of trends.

Postural Stability of Stand-Up Forklift Operators in Response to Normal Braking Procedures

Balance retention and postural stability of forklift operators have not been well investigated in the literature. Our testing shows that forklift operators can maintain postural stability during routine braking procedures while using standup lift trucks, and that peak acceleration levels generated by lift trucks are below the peak acceleration levels mandated by the Americans with Disabilities Act for moving platforms. Our review of studies involving balance retention has shown that acceleration levels experienced by subjects who maintained postural stability were greater than the peak accelerations during forklift braking operation. In addition, acceleration levels alone are a poor predictor of a subject’s ability to maintain postural stability.

MADYMO Simulations of Occupant and Vehicle Kinematics in Offset and Oblique Barrier Tests

Oblique and offset impacts occur more frequently than full frontal impacts and the resulting occupant and vehicle kinematics are more complicated. Simulations of these test modes are more involved with added vehicle degrees of freedom. Additional occupant interactions with the vehicle interior need to be considered so that the occupant kinematics can be correlated more accurately. In order to capture the vehicle motion in an offset or oblique impact, a prescribed motion approach is preferred where the vehicle is given a three-dimensional motion with six degrees of freedom. With a planar motion assumption, the dominant angular motion about the vertical direction can be derived from linear accelerations measured at two locations where the vehicle deformation is a minimum. In a previous study the angular kinematics was given to a coordinate origin located on the vehicle centerline and longitudinally near the rear rocker. The instantaneous center of rotation was assumed to be fixed at this point during the event. This is referred to as Method I in this paper. A new approach, referred to as Method II, applied translational displacement to three bodies, which carried the passenger compartment through stiff spring elements. The displacements were integrated from measured accelerations, eliminating the uncertainty of a shifting center of rotation. Both methods assumed the vehicle frame between the front and rear rockers as a rigid body. The IP and steering column intrusions and floor deformations were neglected. The results from both methods were correlated to a pair of 40 kph 30 degree angle impact tests and an IIHS ODB test. Method II showed a slightly better timing correlation for the angle tests and the IIHS ODB test. However, both methods didn’t predict the lateral head contact for the driver in the left angle test and the passenger in the right angle test. More interior details have to be included in the model to capture the lateral motion of the occupants. The prescribed motion method is a more general approach than the commonly used inverse kinematics method, and can be applied to full frontal impact as well. The versatility of the method provides a basis for a modular approach in occupant simulations.

Design of the SAFER Emergency Gate Using LS-DYNA

In recent years, NASCAR and the Indy Racing League have improved the safety of their racetracks through the installation of the Steel And Foam Energy Reduction barrier (SAFER). The new barrier consists of a high-strength, tubular steel skin that distributes the impact load to energy-absorbing foam cartridges in order to reduce the severity of the impact, extends the impact event, and provides the occupant of the race car additional protection. During installation of the SAFER barrier, the designers realized that certain race tracks were designed with the emergency track exit in the outside of the corner. Because the SAFER barrier needed to be installed in these corners, a gate mechanism had to be designed for the barrier that would provide access to the track while retaining the safety performance of the system. Full-scale crash testing of the first SAFER gate design showed that the gate did not posses sufficient capacity to handle the loads experienced during a worst-case impact scenario. Non-linear finite element analysis was then used to redesign the gate mechanism. The original gate design was simulated using LS-DYNA in order to validate the computational model. Modifications to increase the capacity of the gate mechanism were designed and analyzed until suitable results were obtained through simulation. Finally, the redesigned SAFER gate was successfully full-scale crash tested.

Automated Risk Scenario Generation Using System Functional and Structural Knowledge

Simulation may be the most practical way to assess the risk of systems with complex behaviors such as those that include hardware, software and human elements. However, since under normal design conditions human-designed systems generally perform in familiar and expected ways, a typical simulation will frequently lead to known and anticipated results. As such, the simulation program wastes a lot of time on familiar results without generating new knowledge about the system’s vulnerabilities. In order to increase our knowledge of risk, it would be preferable to push the system toward its limits to test the system’s ability to handle more difficult situations. Such an approach can help system designers to better understand risky situations and close the vulnerability gaps in their design. The primary objective of this study is to develop a risk simulation Planner (SimpraPlan) which generates scenarios that can explore the system’s vulnerabilities and offer a superior assessment of the risks involved. The Planner uses high level engineering knowledge (including the functional requirements and physical structure of the system) to generate scenarios that can exploit the system’s vulnerabilities. In this paper, the scenario generation process is explained in detail and scenarios generated by the SimpraPlan are compared with those generated by classical approaches to risk assessment.