High-tensile bolts without heat treatment

According to DIN-ISO 898-1 high tensile bolts of class 8.8 must have a quenched and tempered structure. Therefore either quenched and tempered wire rod is used for cold heading or the bolts are quenched and tempered after the bolt forming process. This paper presents a new wire rod, which offers the chance to get comparable or even better final properties and lower production costs: a low-carbon MnSi wire rod is used as basic material. The final tensile strength is produced by drawing and cold forming. The conventional final quenching and tempering is omitted and for many cases also baking can be avoided. An increased fatigue resistance and the elimination of final straightening of the bolts are additional advantages of the new process.     

Sintered silicon nitride/nano-silicon carbide materials based on preceramic polymers and ceramic powder

A flexible method is presented, which enables the fabrication of porous as well as dense Si₃N₄/nano-SiC components by using Si₃N₄ powder and a preceramic polymer (polycarbosilazane) as alternative ceramic forming binder. The SiCN polymer benefits consolidation as well as shaping of the green body and partially fills the interstices between the Si₃N₄ particles. Cross-linking of the precursor at 300 °C increases the mechanical stability of the green bodies and facilitates near net shape machining. At first, pyrolysis leads to porous ceramic bodies. Finally, subsequent gas pressure sintering results in dense Si₃N₄/nano-SiC ceramics. Due to the high ceramic yield of the polycarbosilazane binder, the shrinkage during sintering is significantly reduced from 20 to 15 lin.%. Investigations of the sintered ceramics reveal, that the microstructure of the Si₃N₄ ceramic contains approx. 6 vol.% nano-scaled SiC segregations, which are located both at the grain boundaries and as inclusions in the Si₃N₄ grains.     

Supply chain coordination and setup cost reduction in case of asymmetric information

Previous research shows that asymmetric information triggers a decrease of lot sizes compared to the supply chain optimum. Thus, the setup costs per period are suboptimally high. To analyse, whether setup cost reduction can mitigate this effect, we extend the standard framework of lotsizing decisions under asymmetric information by allowing investments in setup cost reduction. We find that asymmetric information tends to lead to an overinvestment in setup cost reduction. The overall effect of setup cost reduction on supply chain performance is therefore ambiguous. We show that these results hold for a wide variety of investment functions.     

Kinetics and dynamics of thermally-induced shape-memory behavior of crosslinked short-chain branched polyethylenes

Systematic investigation of the relation between shape-memory (SM) behavior and characteristics of the covalent network and the crystalline domains of a crosslinked polymer, i.e., crosslink density and crystallinity, respectively, was performed using homogeneous ethylene-1-octenecopolymers (EOC) as model polymers. The EOCs have been crosslinked by 2,5-dimethyl-2,5-di(t-butylperoxy)hexane (DHBP) decomposition. Two EOCs with a degree of branching of 30 and 60 hexyl side chains per 1000C atoms with each four different crosslink densities were employed. The investigated EOCs differ significantly in crystallinity, melting temperature (T_m) and crosslink density. The crosslinked EOC undergone the programming at a strain of 100% showed high strain fixity ratio (R_f) and strain recovery ratio (R_r). The R_f and R_r values increase with increasing crystallinity and crosslink density, respectively, and decline only slightly in a subsequent SM cycle. The switching temperature (T_sw) is strictly related to T_m and decreases with increasing degree of branching as well as crosslink density in the temperature range of 101–63 °C. T_sw remains nearly unchanged when the programming temperature (T_pr) or the load during SM recovery is varied. The kinetics of SM recovery as characterized by the temperature dependence of recovery rate is controlled by the melting behavior. The specific work generated by the programmed specimen during thermally-induced recovery under constant load, gains with increasing crosslink density, and is proposed as dynamical characteristic of practical relevance. The opportunity of tailoring T_sw by variation of the degree of branching and crosslink density makes such polymers attractive candidates for applications requiring T_sw temperatures in the range from 60 to 100 °C.     

Reduced laying depths for supply mains

Laying of supply piping below ground involves heavy costs. This paper from the GDR Bauakademie, Institute of Construction and Civil Engineering, Leipzig, describes how the costs have been reduced by up to 30 percent as a result of reducing the minimum depths required, by reassessing piping statics (interaction of the load ‐ soil ‐pipe system), and the precautions for irregular frost heave, which can be of decisive importance.     

Green manufacturing practices among wooden furniture manufacturers in Malaysia

The adoption of green manufacturing practices by the Malaysian wooden furniture industry is limited as is shown by a questionnaire-based survey of wooden furniture manufacturers. The lack of price premium for green furniture products and the high cost involved in adopting such practices have been identified as the major restraints. Currently most green manufacturing practices are related to the use of environmental-friendly materials.