BALTIMORE -- The Center for Nondestructive Evaluation at Johns Hopkins University is helping American firms increase their productivity and competitiveness by catching and eliminating design flaws during the manufacturing process.

"We're not only looking at things after they're finished; we look at them as they're making them," said Robert Green, director of the center. He describes the center's basic mission as improving quality control for industry.

Using $25,000 annual dues paid by each of 20 industrial firms, as well as grants and consulting fees, the center helps design ship hulls that won't leak, pacemaker batteries and heart valves that will last and gas pipelines that won't corrode easily. In addition, it can use special techniques to determine if airtight drug packaging has been tampered with.

The one requirement for the center's clients: that they be American firms.

The concept of nondestructive evaluation is simple. It probably originated with tests as simple as listening to a bell to make sure it rang true, or looking at newly blown glass for visible flaws.

Today, scientists perform tests that extend the range of sight and sound to detect defects early without having to take the object apart or destroy it. They use such techniques as ultrasound, infrared examination to detect release of heat, holography to produce three-dimensional images, X-rays, and lasers, to see where products are weak.

A collection of 35 faculty and senior staff members, 50 graduate students and about 25 undergraduates work on the center's projects, often in conjunction with Hopkins' Applied Physics Laboratory in Howard County, the Department of Biomedical Engineering at the Johns Hopkins School of Medicine and the undergraduate school of Arts and Sciences.

The center has developed its own special technique of detecting leaks using three-dimensional imaging that compares the superimposed image of an object and the object itself after it is subjected to high pressure. It's also using a technique called electron spin resonance to pick up defects in polymers.

Other projects in the works include development of sensors that feed information into computers to adjust and correct production before it's completed. The principal areas of concentration are aerospace technology, microelectronics, energy production and surgical implants. In addition, the center has branched out into such areas as art conservation, helping to date antique materials and uncover changes in canvases.

The director noted that not all testing can be nondestructive.

"Some things have to be destroyed to make sure what you measure nondestructively" is correctly calibrated, Green said.