Hikmat F. Mahmood

Service Life Heat Exposure Effects and ALuminm Aluminum Extrusion Crash Properties Relationship Under Static Axial Loading

Relationship between service life heat exposure and extruded aluminum structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum alloy extrusions each of which is subjected to two heat treatments. The aluminum extrusion investigated are 6063T6, 6061T6, 6260T6, 6014T6, and 7129T6. The two heat treatments are 177°C for 30 minutes and 200°C for 24 hours. The 200°C/24 hours treatment represents the most severe thermal exposure i.e. components adjacent to exhaust pipes and manifolds. The 200°C heat treatment is in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. These ten crash members were subjected to static axial crushing at a speed of 25.4 mm/minute (1 in/min). Force-time data was collected and responses were plotted for all tests. Force-displacement responses were integrated for the crush energy management and mean axial crush load for each of the aluminum extruded crash members. Bar charts were then generated to describe the crush loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Severe service life simulated heat exposure was found to affect the mean crush load and crush energy management of the aluminum structural crush members. The heat exposure effects on the crashworthiness of the extruded aluminum members ranged from a reduction of 8% to over 20% in the mean crush load and crush energy management with highest variation observed with the 6260T6 aluminum extrusion.Copyright

Design of a Frontal Rail Structure With Thickness Variation That Performs Under Axial and Oblique Loading

Progressive crushing of the frontal part of the frame in any collision (frontal, offset and oblique) is one of the factors that determine the safety level that a car or a truck can provide to the occupant. A new approach in frontal rail design will be covered in this paper. The rail thickness will vary along the length of the rail in such away that the compressive strength of a rear section on the compression side of the rail will be greater than or equal to the section in front of it. This design will enable the front rail to collapse in a progressive manner such that the collapse will be transmitted from the front to the rear. Preventing early global bending in the rail will enhance the efficiency of energy absorbed during a crash. Starting with the section with the lowest compressive strength (most forward section of the rail), in a controlled way, the section strength is designed to increase with length. This will help meet the federal regulations such as FMVSS 208 by collapsing the least strong front sections at lower speeds and the strong rear sections at higher speeds. Also, collapsing of the weak frontal sections in a crash can help in compatibility between different vehicles on the road.Copyright

Service Life Aging and Heat Exposure Effects on Aluminum Sheet Alloy Properties and Structural Crashworthiness Under Dynamic Axial Loading

An investigation of the service life aging and heat exposure effects on sheet aluminum alloy properties and structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum sheet alloys each of which is subjected to four heat treatments. The aluminum sheet alloys investigated are 6111T4PD, 5754-O, 5182-O, 6022T4E29, and 6022T4. The four heat treatments are 177°C for 30 minutes, 200°C for 15 minutes, 200°C for 2 hours, and 200°C for 24 hours. The 200°C/24 hours treatment simulates the most severe thermal exposure i.e. components adjacent to exhaust pipes and manifolds. All 200°C heat treatments are in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. Aluminum rails of hexagonal cross-section were formed for the twenty combinations of aluminum sheet alloys and heat exposures. These twenty formed aluminum rails were then bonded and riveted using Betamate 4601 adhesive and Henrob K50742 self-piercing rivets. Once assembled, these twenty rails were subjected to dynamic axial crushing at a speed of 40 kph (25 mph). Force-Time data was collected and responses were plotted for all tests. Force-Displacement responses were then integrated for the crush energy management and mean axial crush load for each of the aluminum sheet rails. Bar charts were generated to describe the crash loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Service life simulated heat exposure was found to affect the mean crash load and crash energy management of the aluminum structural crash members. The heat exposure effects on the crashworthiness of the sheet aluminum members ranged from a reduction of [−21.6%] to an increase of [+6.8%] in the mean crash load and crash energy management with higher variation observed in the “T4” tempered aluminum alloys.Copyright

Crashworthiness of Aluminum Extrusion Under Simulated Service Life Heat Exposure

An investigation of the service life aging and heat exposure effects on extruded aluminum alloy properties and structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum alloy extrusions each of which is subjected to two heat treatments. The aluminum extrusion investigated are 6063T6, 6061T6, 6260T6, 6014T6, and 7129T6. The two heat treatments are 177°C for 30 minutes and 200°C for 24 hours. The 200°C/24 hours treatment represents an upper limit thermal exposure i.e. components adjacent to exhaust pipes and manifolds. The 200°C heat treatment was applied in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. These ten crash members were subjected to dynamic axial crashing at a target speed of 40 kph (25 mph). Force-time data was collected and responses were plotted for all tests. Force-displacement responses were then integrated for the crash energy management and mean axial crash load for each of the aluminum extruded crash members. Bar charts were then generated to describe the crash loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Service life simulated heat exposure was found to effect the mean crash load and crash energy management of the aluminum structural crash members. The heat exposure effects on the crashworthiness of the extruded aluminum members ranged from a reduction of 10% to over 20% in the mean crash load and crash energy management with highest variation observed with the 6260T6 aluminum extrusion.Copyright

Crashworthiness Challenges in Steel-to-Aluminum Front End Design

The search for weight reduction opportunities to improve corporate average fuel economy has led the auto industry to investigate light weight materials such as aluminum and magnesium. These materials can reduce vehicle weight while satisfying crash safety requirements of corporate, government, and independent insurance agencies. As a result, designs of several vehicles have been fully migrated from steel to aluminum while many other vehicles have opted to substitute lighter materials at the component and system levels. An investigation has been conducted on the front end principal crash energy absorbing rails to convert the original HSLA350 steel structural members into 5754NG aluminum. The investigation shows that while the substitution of aluminum at the right thickness can achieve lighter weight and higher specific energy, additional design parameters such as design load targets remain a major challenge. A comparison of steel versus aluminum mean crash loads, crash energy management, weight saved, specific energy, and design load target highlights some of these challenges. The results from an experimental investigation of stamped 5754NG aluminum sheet rails show the substitution of stamped 5754NG aluminum sheets for steel rails reduces the weight of each of the front rails by 3.3 (lb) and enhances the specific crash energy management efficiency by 38%. To solve the design load target challenge, the same investigation extends to higher strength 6xxx series extruded aluminum material using CAE modeling and demonstrates an increase in crash energy management efficiency of up to 80%.Copyright