CASE STUDY | Work Lamp Analysis

HELLA New Zealand is at the forefront of the Road Transport, Automotive and Safety Lighting industry, specialising in LED Lamps. HELLA New Zealand designs and manufactures a vast range of products to automotive manufacturers and commercial transport fleets globally and provide aftermarket replacements and upgrades for many applications.

THE CHALLENGE

HELLA was developing a new HypaLUME LED work lamp for use in extreme outdoor environments such as on mining vehicles, rock crushers, and road works generators—environments where they’d be exposed to the elements and subjected to varying vibrational loads.

A new die-cast side bracket design had been introduced for mounting the individual lamp assemblies. HELLA was concerned about possible excessive stresses in the primary mount bracket and the new side brackets caused by the environmental vibrations existing at frequencies close to the product’s natural resonant frequencies.

Caliber was approached to provide confidence in the bracket design while avoiding the high costs of prototyping and physically testing many design iterations.

THE SOLUTION

A modal analysis was carried out first to determine the assemblies’ natural frequencies, to ensure the frequencies are far enough away from expected real world conditions. This quick test is vital to ensure the assembly will not experience unexpected early fatigue failure due to large alternating stresses if the two frequencies are too close. Linear static analysis was performed to establish the design stress margins and fatigue life capability of the parts in question.

The initial analysis determined a need to move resonant frequencies away from the expected operational conditions. A series of updated models were provided by HELLA based on modal analysis results until a resonant frequency more than 2.5x the maximum expected excitation frequency was achieved. With this done, the static tests could be confidently performed using the maximum expected acceleration under environmental vibration to verify the parts against their applicable stress limits. The FEA analysis was backed up by hand calcs to verify the results.

The same analysis was performed on the existing product (shown) to aid in verification of the FEA set up against existing test data. The project ended with a detailed FEA report and recommendations from Caliber on the best design to use for product durability and longevity.

The project was successfully completed within the planned time budget, with sufficient room in the budget to perform further analysis on additional load cases and some alternative designs. This gave HELLA even more confidence in their design.

The process ensured the vibrational characteristics and expected stresses in the product were fully understood. The design was quickly modified to tackle the problem areas, before incurring any prototyping costs such as castings, assembly, labour, and testing. This analysis work was unaffected by changes in Covid-19 alert levels.